Most people are familiar with birthday balloons. Rubber balloonsare filled with helium or air and come in a variety of colors.Mylar balloons are most often filled with helium; they have ametallic sheen, and have a variety of designs printed on them.Rubber balloons are also called latex balloons. These balloonsoften do not last long, because the helium leaks out through tinypores in the rubber. Filling the balloon with plain air will causeit to last much longer, but of course, such balloons will notfloat. On the other hand, you may not want your balloons to lastlong past the birthday celebration; random balloons floating aroundthe house can be annoying. If you do want them to last, however,and you prefer rubber balloons, you can ask if your store has anyballoons that have been treated with